Be careful with this, when you wire in the fusebox on your truck you'll get 12 volts - and many GPS systems (like the Garmin) use 5 volts. The cig. lighter adapter has a converter in it to bring the power down to a safe level. If you cut the end off you also cut off the converter and you can damage the unit that way. Better to use a female cig. lighter socket to wire in to the fuse box, and then just plug the adapter into the socket behind the dash.
I am an installer at my local Best Buy and while I can vouch for all the people at my store, I do know there are many stores out there that do shady work. Some good things, all Best Buy locations require all of their installers to be MECP certified, where most of the smaller shops do not. Also, Best Buy is a large company and can literally afford to purchase you a new truck if the installer were to damage it that much. The lifetime labor warranty guarantees that if anything bad should happen to the GPS or the truck due to a sloppy install they will pay to take care of it. I know 100% that Best Buy isn't going anywhere (even with the economy situation Best Buy is still growing) but who knows about those smaller shops.
Talk to the installers at your local Best Buy and at some of the other places to get a feel. If the guy seems nice and sounds like he knows what he's talking about, I'd go for it. The lifetime warranty is comforting. Just some food for thought.